Method for the wireless and contactless transport of energy and data, and corresponding device

ABSTRACT

In installations including fixed and mobile structural elements and a rotary current motor as a drive, the rotary current motor can be used for the wireless transmission of both energy and/or data. The transmission from the fixed structural elements to the mobile structural elements of the rotary current motor is especially inductive. In the corresponding device including a rotary current motor including a stator and a secondary element, the secondary element is not embodied as a solid conductor with or without a laminated core, according to prior art, but rather as a laminated core including integrated windings which is the same as, or similar to, the stator.

This application is the national phase under 35 U.S.C. § 371 of PCTInternational Application No. PCT/DE2003/002854 which has anInternational filing date of Aug. 27, 2003, which designated the UnitedStates of America and which claims priority on German Patent Applicationnumber DE 102 40 080.6 filed Aug. 30, 2002, the entire contents of whichare hereby incorporated herein by reference.

FIELD OF THE INVENTION

The invention generally relates to a method for wire-free or wirelessand non-contacting or contactless power/energy and data transport.Additionally, it generally relates to such a method in systems whichinclude fixed and moving structural parts, preferably including athree-phase motor as a drive for the moving structural parts. Thethree-phase motor may in this case be in the form of a rotating motorand, in particular, a linear motor as well. The invention also generallyrelates to an apparatus for carrying out the method, preferably having athree-phase motor which includes a stator and rotor or linear secondarypart—both of which are referred to in the following text just as asecondary part.

BACKGROUND OF THE INVENTION

Transport devices are frequently driven directly by linear motors. Inthis case, it is necessary to transmit power and information to thedriven components in order in turn to be able to carry out specificfunctions there, such as loading and unloading, and to supply devicesfor this purpose.

Problems relating to such devices, especially with linear motors, willbe explained in the following text using an example. A piece goodstransport device includes a large number of vehicles which themselvescarry various goods, such as packages, postal items etc. The vehiclesmove on predetermined paths, such as rails or the like, and are drivenby one or more linear motors (LIM).

One or more stators of these linear motors (LIM) is or are fitted in afixed position or positions between the rails. The secondary parts ofthe linear motors (LIM) are attached to the vehicle to be driven and, byway of example in the case of an asynchronous three-phase LIM in thesimplest case, include a solid conductor, for example aluminum orcopper, but are often also equipped with a laminated core behind thissolid conductor in order to improve the magnetic return path. When thevehicle with the secondary part of the linear motor (LIM) moves over thefixed stator a driving force acts on the vehicle as a result of the LIMprinciple, which is known per se. Since the vehicles are coupled to oneanother, even vehicles which are not being driven at any given time andare accordingly located between two stators are driven.

By way of example, in order to sort packages, the vehicles have to pickup and deposit piece goods in order that the transport device can carryout its correct task. For this purpose, the trucks have a conveyordevice, for example a conveyor belt with an electrical drive or thelike, which can pick up and place down the piece goods at specificpoints transversely with respect to the movement direction of thevehicle. On the one hand, power is required for this drive located onthe vehicle. On the other hand, it is necessary to signal in somesuitable manner to the drive when and in what way piece goods should bepicked up or placed down. Furthermore, it may be necessary to transmitinformation from the vehicle about the piece goods, for example theweight, size, shape, code read from the piece goods, etc., to a fixedcontroller for the transport device.

It is known from the prior art, for moving parts of a transport deviceto be supplied with electrical power and for the communication with suchmoving parts to be organized via sliding contacts as well as slidingcontact lines fitted to the movement path. Both the sliding contacts andthe sliding contact lines are subject to a certain amount of wear.

Accordingly, both the sliding contacts and the sliding contact linesrequire intensive maintenance. Furthermore, the sliding contact linesand the sliding contacts make up a considerable proportion of the totalcosts of the transport device.

One example of the need to transmit power and information to rotatingcomponents is that for measurements directly on rotating structuralparts. This is the situation, for example, for torque determination, inwhich strain gauges are used to determine the torsion on the shaftresulting from the torque. On the one hand, the rotating measurementdevice and signal processing require power, while on the other hand themeasured value must be transmitted to the fixed part of the system.Further examples occur with the operation of magnetic bearings or thecontrol of rotating field windings.

According to the prior art, power and data are transmitted to rotatingstructural parts via slip-rings with associated sliding contacts. Thisis associated with the disadvantages which have already been mentionedfurther above. In particular for data transmission to rotatingcomponents, telemetry devices are known, although these arecorresponding costly.

U.S. Pat. No. 6,326,713 B1 discloses an electrical machine and a methodfor transmission of power between the different systems, in particularthe stator and the rotor of the machine, in which power is transmittedinductively. The electrical machine is modified for this purpose, andspecial coils with suitable inductances are provided. Furthermore, DE199 32 504 A1 describes the provision of non-contacting power and datatransmission between two parts which can rotate with respect to oneanother, with the transmission path for power and data transmissioncomprising two or more coils which are mounted such that they can rotatewith respect to one another. For power transmission in themedium-frequency range from a primary stationary conductor to movingsecondary loads, DE 42 36 340 A1 provides for the secondary conductorsto have coils which are rotated about the primary energy producer with acoil. The same principle of inductive power transmission from one coilto another coil is disclosed in WO 01/88931 A1.

Furthermore, U.S. Pat. No. 5,521,444 A discloses a device fortransmission of electrical power from a stationary device element to arotating device element, without any direct contact.

SUMMARY OF THE INVENTION

An object of an embodiment of the invention is to specify an improvedmethod which can be used equally well for power and data transport, andto provide an associated apparatus.

An embodiment of the invention provides an improved capability totransmit power on the one hand and data as information on the other handfrom fixed components of a system to moving components of the system,and to functional control devices there. This may be advantageous, inparticular, for transport devices with a linear motor. However, it canalso be used for systems with rotating parts. Functions can thus becarried out with accurate data on the driven parts of the system.

An embodiment of the invention may avoid at least one of thedisadvantages of the prior art as mentioned above, since the three-phasemotor, which may be provided in any case in order to drive the movingcomponents, may be at the same time used to transit power and data. Anidea of an embodiment of the invention is not only to design thesecondary part as a solid conductor with or without a laminated core,but in fact to use a laminated core which is the same as or similar tothe stator and has windings inserted in it as the secondary part, aswill be explained further below with reference to FIG. 1 and FIG. 2. Afeature for the production of a translational force in an embodiment, isthat the stator and secondary part have the same number of pole pairsand pole pitches. However, the stator and secondary part may havewindings with different numbers of turns and a different cross section.

BRIEF DESCRIPTION OF THE DRAWINGS

Further details and advantages of the invention will be found in thefollowing description of the figures and description of exemplaryembodiments, with reference to the drawings, in which, in each caseillustrated schematically:

FIG. 1 shows the basic design of the stator and secondary part of alinear motor,

FIG. 2 shows the basic design of the stator and rotor of a rotatingthree-phase motor,

FIG. 3 shows the circuitry for the stator and secondary part of thethree-phase motor shown in FIG. 1,

FIG. 4 shows circuitry, modified from that shown in FIG. 3, for thestator and secondary part of the three-phase motor shown in FIG. 1;

FIG. 5 shows power being supplied to a single vehicle in a transportsystem,

FIG. 6 shows a power bus for supplying all the vehicles,

FIG. 7 shows the inputting and outputting of high-frequency signals inorder to transmit data between the stator and secondary part of thethree-phase motor, and

FIG. 8 shows the complete data and power bus system.

Identical elements have the same reference symbols in the individualfigures. In some cases, the figures will be described jointly in thefollowing text.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

FIG. 1 shows the major parts of a linear motor. A fixed stator isannotated 10, while, in contrast, the secondary part of the linearmotor, which moves relative to it, is identified by 20. The stator 10and the secondary part 20 have winding sections a, b and c which areconnected in different combinations ±a, ±b and ±c, where + and − denotethe respective current flow direction, to the phases L1, L2, L3 whichare used as the supply lines for the windings.

FIG. 2 shows the corresponding parts of a rotating three-phase motor. Afixed stator is in this case annotated 10′ while, in contrast, thesecondary part which moves relative to it as the rotor is identified by20′. The stator 10′ and rotor 20′ once again have winding sections a, band c, which are connected in different combinations ±a, ±b and ±c,where + and − denote the respective current flow direction, to thephases L1, L2, L3, which are used as supply lines for the windings.

In FIGS. 3 to 8, the windings for the stator 10 are annotated 11 to 13,and those for the secondary part 20 are annotated 21 to 23. A motorcontroller 30 is connected between the power supply system feed with thephases L1, L2, L3 and the windings 11 to 13.

FIG. 4 shows a corresponding situation, but with a harmonic being usedto supply the secondary part in this case. When used correctly for atransport apparatus with moving vehicles 50, 50′ . . . 50 ^(n′), thestator 10 is part of a track or rail system, which is not illustrated inthe drawing, and the secondary part 20 is part of a single vehicle 50.The individual vehicles 50, 50′, . . . 50 ^(n′) are in this casephysically identical.

Power is transmitted from the stator 10 or 10′ to the respective movingsecondary part 20 or rotor 20′ as illustrated in the form of a circuitdiagram in FIG. 3 in which, in particular, the parts 10 and 20 areidentified, and this is done on the following principle:

The three windings 11 to 13 of the stator 10 are connected in the normalmanner to the three-phase power supply system or to a three-phase motorcontroller 30, for example a frequency converter or a three-phasecontroller. The three windings 21 to 23 of the secondary part 20 areconnected in star or delta. The free ends of the windings 21 to 23 areconnected by means of diodes D1 to D6 to a six-pulse rectifier 24 whenthey are connected in star, and their nodes are connected by means ofdiodes D1 to D6 to a six-pulse rectifier 24 when they are connected indelta. In certain conditions, AC voltages are induced in the windings 21to 23 of the secondary part 20 as a result of the induction caused bythe stator 10. These voltages are converted in the rectifier 24 to a DCvoltage, which produces a pulsating direct current when a load isapplied to the rectifier output.

The direct current is first of all supplied to an energy storageelement, such as a supercap, a rechargeable battery or the like, but inparticular a capacitor 28 with a capacitance C, via a further diode 26.Initially, the capacitor 28 represents a short circuit, since itsvoltage is U_(c)=0. In this case, the situation is accordingly similarto that of a squirrel-cage rotor for an asynchronous motor. As thecurrent flows, the voltage across the capacitor 28 rises in proportionto the amount of charge. When a specific voltage, as is required forsupplying power to the vehicle 50, is reached, then the switch 25 isclosed, thus resulting in a short-circuited rotor for the linear motor,once again. This prevents further charging of the capacitor C, and thevoltage across the capacitor remains constant or falls when loads in thevehicle 50 are fed from the charge in the capacitor 28. When the switch25 is closed, the diode 26 prevents the capacitor 28 from beingdischarged via the switch 25.

When the voltage across the capacitor 28 now falls below a specificthreshold value as a result of being discharged through the loads on thevehicle 50, as shown in FIG. 5, the switch 25 is opened again, and thecapacitor 28 with the capacitance C is charged again. As the procedurecontinues, the voltage across the capacitor 28 is thus regulated betweenan upper and a lower limit value by operation of the switch 25.

In one particularly advantageous embodiment, the switch 25 is atransistor, in particular a field-effect transistor. A transistor suchas this allows very high switching frequencies to be achieved, thusresulting in a quasi-steady-state voltage across the capacitor 28, whichcan be used for supplying power to the vehicle 50.

Suitable control algorithms are used to activate the switch 25 in such away that the voltage across the capacitor 28 is kept virtually constantindependently of the power drawn and of the speed of the secondary part20.

In a first embodiment of this procedure, only the voltages induced bythe translational slip in the secondary part are used for charging thecapacitor 28. To do this, the speed of the secondary part has a certainamount of slip with respect to the traveling field of the stator. Thisslip is additionally provided to the slip component which transmits thepower from the stator 10 to the secondary part 20.

In one variant of the procedure explained above, the voltage across thecapacitor 28 is kept in the region of a few volts in order to minimizethe additional slip which occurs in principle as a result of the powertransmission, with this voltage subsequently being raised to therequired level in a DC/DC converter.

In a further option for power transmission, as is illustrated in FIG. 3,a current which is identical in each of the three windings 11 to 13,that is to say in each case has the same phase angle, is superimposed onthe three windings 11 to 13 of the stator 10 in addition to the threecurrents which are at the power supply system frequency and have phaseangles of 120° between them. This current is also referred to as theneutral current, because the stator star point must be connected for itsreturn path. The neutral current that is applied is preferably at ahigher frequency than the power supply system frequency.

If this neutral current has the same phase angle in all three windings,then this results only in a field which varies with time, but in atraveling field. No additional shear forces are thus produced either, bythe higher-frequency currents.

In the latter variant, both the windings 11 to 13 of the stator 10 andthe windings 21 to 23 on the secondary part 20 must be connected instar, with an accessible star point, in order to provide the return pathfor the neutral current. The magnetic field from the stator windings 11to 13 once again induces a voltage in the three short-circuitedsecondary winding elements 21 to 23, which voltage can be used in themanner already described via a two-pulse rectifier for charging of thecapacitor 28 with the capacitance C, and thus for supplying power to thevehicle 50. This method has the advantage that the amount of power whichcan be transmitted is largely independent of the slip between thesecondary part 20 and the traveling field of the stator 10.

If, by way of example, a neutral current is fed in in the mannerdescribed above, then the circuitry of the stator 10 and secondary part20 must be modified as shown in FIG. 3.

In this case, there is no need for charge regulation, because thevoltage across the capacitor 28 cannot exceed the transformed value ofthe applied harmonic. The forward movement of the transport device thatis produced as well as the power supply for the transported device canthus be controlled independently of one another.

In transport devices, the stator 10 is generally supplied viaconverters, for example the motor controller 30. The abovementionedfrequency component can be produced without any additional hardwarecomplexity by suitable modification of the control method, for examplesuitable modulation of the voltage space vector, for the converter.

Both the power transmission principles described above operate not onlywhen the secondary part 20 is in the area of the induction field of thestator 10. However, this is true only when the vehicle 50 in FIG. 5 isstopped with the secondary part 20 precisely above a stator 10, or ismoving over it. In order to ensure the power supply to the vehicle 50even when the vehicle 50 is not located above a stator 10 at that time,a rechargeable energy store 40 which, for example, may once again be asupercap or a rechargeable battery, is additionally fitted to eachvehicle 50 in order to stabilize the supply voltage. The energy store 40is charged when the vehicle is located above the stator, and is thenused as the energy source for supply power to the vehicle when thevehicle is between two stators. In this case, it is necessary to ensurethat the ratio of the power to be supplied while located above thestator 10 to the average power required between two stators 10, 10′during motion is higher than the ratio of the movement time to thestationary time. The transport device must therefore move continuously.

In a further embodiment as shown in FIG. 6, the power supplies for thevehicles 50, 50′, . . . 50 ^(n′) can be connected to one another. Thisis possible because the vehicles 50, 50′, . . . 50 ^(n′), in any caseform an essentially closed chain because, if this were not the case, thevehicles which are not being driven at that time would remainstationary. The connection of the power supplies to the vehicles resultsin a power bus, so that vehicles which are currently located above astator also provide the power for vehicles which are currently betweentwo stators 10, 10′. This allows the energy stores 40 on each vehicle50, 50′, . . . 50 ^(n′) to be considerably smaller, or else to beomitted completely. A further advantage is that all the vehicles 50,50′, . . . 50 ^(n′) can be supplied with power for an indeterminate timeeven when the transport device is stationary.

FIG. 7 shows data being transmitted from the fixed part to the movingpart of the linear motor, that is to say from the stator 10 to themoving vehicles 50, 50′, . . . 50 ^(n′), and vice versa, on the basis ofthe following principle: The inductive coupling between the stator 10 asthe primary part and the secondary part 20 is likewise made use of. Thedata is modulated in some suitable form, which is known in acorresponding manner from the prior art, and is transmitted in the formof signals at a considerably higher frequency than the power supplysystem frequency. Any desired methods such as PSK, FSK, OFDM, CDMA orfrequency hopping, etc., may be used as the modulation method.

On the stator side, the operating voltage, which is at the power supplysystem frequency, has the high-frequency signal for transportation ofthe data superimposed on it. A so-called coupling unit 60 is used forthis purpose, which essentially comprises a high-frequency transformerwith four windings 61 to 64 as well as three coupling capacitors 66 to68. When the three windings on the power supply system side of thehigh-frequency transformer 61 to 63 are being connected, care must betaken to ensure that the coil connections are oriented in the same waywith respect to the winding starts, in order that the high-frequencymagnetic fields do not cancel one another out in the air gap in thelinear motor.

As is shown in detail in a particularly advantageous manner in FIG. 6,the star point of the three stator windings 11 to 13 is advantageouslyin each case connected to the other winding end. If the stator 10 isconnected in delta, each winding 11, 12, 13 on the stator 10 isconnected to a respective winding 61, 62, 63 on the high-frequencytransformer such that the fields reinforce one another.

However, all other inputting methods which are known according to theprior art may in principle also be used. A corresponding procedure isused on the secondary part side, by the essentially identical couplingunit 60 being connected in the same manner to the winding ends of thesecondary part 20. The fixed component also has a coding device 35 witha modulator/demodulator and a controller 45, while the moving componenthas a coding device 35′ with a modulator/demodulator and a controller4′.

FIG. 8 shows a combined data and power bus system for the stationaryarea with stators 10 on the one hand, and the moving area with secondaryparts 20 and vehicles 50 on the other hand. In this case, a sensor 78 isalso fitted to each secondary part 20 and detects when a single vehicle50 is located above the stator 10. When a vehicle 50 is detected abovethe stator 10, then the controller for the moving components allows theassociated coding device to transmit message telegrams. The vehicle 50itself identifies incoming data telegrams and, after successfulreception of a telegram from the stator 10, can itself transmit a datatelegram via the stator 10 to the fixed controller with electronics 70.

In order additionally to transmit data to vehicles 50 which are notlocated above a stator 10, all of the vehicles 50, 50′, . . . , 50 ^(n′)as shown in FIG. 8 can be connected to one another by way of a data lineor a data bus 76. Furthermore, each telegram is preceded by a uniquedestination address, so that the message recipient can be identified.When a vehicle 50 now receives a data telegram which is not intended forit, it transmits this data telegram to the data bus 76. The telegramtraffic on the data bus 76 can from then on continue on the basis of theCSMA/CA, CSMA/CD or master/slave principles, which are known fromfieldbus systems. A power bus 71 on the one hand and a data bus 72 onthe other hand can likewise be provided on the stator side.

In the arrangements which have been described with reference to theindividual figures, the major technical advantages are that there is nolonger any need for sliding contacts and sliding contact lines fortransmission of power and data. This results in a system which is verylargely maintenance-free.

Exemplary embodiments being thus described, it will be obvious that thesame may be varied in many ways. Such variations are not to be regardedas a departure from the spirit and scope of the present invention, andall such modifications as would be obvious to one skilled in the art areintended to be included within the scope of the following claims.

1. A method for wireless and non-contacting power and informationtransport in systems which include fixed and moving structural parts anda three-phase motor as a drive for the moving structural parts,comprising: using the three-phase motor in the same way for wirelesstransmission of power and information; and supplying devices, arrangedon the moving structural parts of the system, with at least one of powerand information.
 2. The method as claimed in claim 1, wherein thethree-phase motor includes a stator and a secondary part, and whereinthe power is transmitted via the inductive coupling between the statorof the three-phase motor and the secondary part of the three-phasemotor.
 3. The method as claimed in claim 2, wherein a slip, presentbetween the stator and the secondary part, is used to transmit powerfrom the stator of the three-phase motor to the secondary part of thethree-phase motor.
 4. The method as claimed in claim 2, wherein analternating current, whose frequency is higher than the fundamental, andis preferably three times the power supply system frequency, is appliedto the stator, in order to transmit power from the stator of thethree-phase motor to the secondary part of the three-phase motor.
 5. Themethod as claimed in claim 1, wherein the information is transmitted viainductive coupling between the stator part and the secondary part, withthe data being modulated and being transmitted in the form of signals ata considerably higher frequency than the power supply system frequency.6. An apparatus, comprising: a three-phase motor which includes a statorand a secondary part, wherein the stator and the secondary partrespectively have three-phase windings with the same number of polepairs and with the same pole pitch.
 7. The apparatus as claimed in claim6, wherein the three-phase motor is a linear motor.
 8. The apparatus asclaimed in claim 6, wherein the three-phase motor is a rotating motor.9. The apparatus as claimed in claim 6, wherein the windings of thestator are connected to at least one of the three-phase power supplysystem and to an associated motor controller, with the windings of thesecondary part being connected in star or delta.
 10. The apparatus asclaimed in claim 9, wherein the motor controller is a frequencyconverter.
 11. The apparatus as claimed in claim 10, wherein the freeends of the windings of the secondary part are connected to a 6-pulserectifier if connected in star, and the nodes of the windings of thesecondary par are connected to a 6-pulse rectifier if connected indelta.
 12. The apparatus as claimed in claim 6, wherein an energystorage element whose energy storage state is controllable is providedfor power transmission.
 13. The apparatus as claimed in claim 12,wherein the energy storage element is a capacitor.
 14. The apparatus asclaimed in claim 6, wherein the voltage across the energy storageelement kept virtually constant via a controllable switch, independentlyof the power drawn and of the speed of the secondary part.
 15. Theapparatus as claimed in claim 6, wherein a coding device is provided fortransmission of data as information.
 16. The apparatus as claimed inclaim 15, wherein a control device enables the coding device to transmitmessage telegrams.
 17. The apparatus as claimed in claim 6, wherein atleast one coupling unit is provided.
 18. The apparatus as claimed inclaim 16, wherein the coupling unit includes a high-frequencytransformer with four windings, and three coupling capacitors.
 19. Theapparatus as claimed in claim 7, wherein at least one transport vehicleis provided above the stator of the linear motor, and wherein sensorsare provided, by which the location of the vehicle above the stator isdetectable.
 20. The method as claimed in claim 2, wherein an alternatingcurrent, whose frequency is three times the power supply systemfrequency, is applied to the stator, in order to transmit power from thestator of the three-phase motor to the secondary part of the three-phasemotor.
 21. An apparatus for carrying out the method of claim 1,comprising: the three-phase motor, including a stator and a secondarypart, wherein the stator and the secondary part respectively havethree-phase windings with the same number of pole pairs and with thesame pole pitch.
 22. The apparatus as claimed in claim 12, wherein theenergy storage element is a at least one of a so-called supercap and arechargeable battery.
 23. An apparatus, comprising: a three-phase motor,including a stator and a secondary part, wherein the stator and thesecondary part respectively have three-phase windings with the samenumber of pole pairs and with the same pole pitch, and wherein thethree-phase motor is useable in the same way for wireless transmissionof power and information.
 24. The apparatus as claimed in claim 23,wherein the three-phase motor is useable as a drive for movingstructural parts and for supplying devices, arranged on the movingstructural parts, with at least one of power and information.